The present invention relates to electrically operated hydraulic actuators which, in response to an electrical control signal cause an electrically operated valve device to control the flow of pressurized hydraulic fluid to a pressure responsive actuator for performing a desired function. Electro-hydraulic actuators are found in widespread usage with a solenoid operated valve employed as the electrically responsive control device for pressurizing piston or diaphragm type pressure responsive actuators.
Recent demands for increased fuel economy and reduced emissions from internal combustion engines, particularly for motor vehicle applications, have resulted in the development of systems for selectively deactivating the combustion chamber valves in multi-cylinder engines during operation in order to disable combustion in certain of the combustion chambers. This arrangement has been found to be desirable where relatively large displacement multi-cylinder engines are employed in vehicles requiring substantial engine power during portions of the operating cycle but substantially less power in other portions of the cycle. For example, during the idling portion of the operating cycle it is not required that combustion occur in all cylinders of the engine to maintain engine operation. However, when acceleration or power to maintain speed on a grade is required, it is then desired to engage all combustion chambers for firing.
Heretofore, systems for selectively deactivating combustion chamber valves during engine operations have provided for releasable latch mechanisms in the valve gear train of cam operated combustion chamber valves. Such latches, upon release, permit lost motion of the valve gear components which prevents valve movement or xe2x80x9cliftxe2x80x9d of the combustion chamber poppet valves from their closed position against the valve seats. Early forms of engine valve deactivators employed an electric actuator such as a solenoid for moving a latch holding the pivot fulcrum of each valve; and, thus one electrical actuator was required for each valve to be deactivated. This arrangement proved to be not only relatively costly for high volume motor vehicle engine production but also consumed a prohibitive amount of space or volume and often required enlarged valve gear covers of the engine which created problems in packaging the original in the vehicle engine compartment. Therefore, it was desired to provide a way or means of reducing the number of electrical actuators required for effecting deactivation of selected combustion chamber valves. Furthermore, the amount of electrical power required to operate the number of solenoids required to deactivate the desired number of valves, as for example, up to half of the number of combustion chamber valves in the engine, placed a prohibitive burden upon the engine electrical power source which is typically relatively low voltage in the range of 12 to 14 volts direct current.
Thus, it has been desired to provide a way or means of reducing the number of solenoids and the size of the solenoids required for selective combustion chamber valve deactivation and yet provide the speed of actuation for movement of the valve deactivating latch mechanism during the cam dwell or base circle period at the engine speed.
It has been proposed to use electro-hydraulic actuators for engine valve deactivation. However, such an arrangement employs a solenoid operated valve for each hydraulic actuator for each valve. This letter arrangement would reduce the power requirements for each solenoid but does not reduce the number of solenoids for each engine valve to be deactivated and thus does not enable engine valve deactivators to be utilized without sufficiently increasing the volume of the engine.
Broadly, the present invention provides an electro-hydraulic actuator of the type employing a solenoid operated valve for controlling flow of pressurized hydraulic fluid to a pressure responsive actuator. More particularly, the electro-hydraulic actuator of the present invention includes a block having a plurality of bores with moveable pistons therein connected to a common valving chamber to which pressurized hydraulic fluid is valved by a single solenoid operated valve. Each of the pistons is connected respectively externally of its bore to an actuator member adapted for operatively contacting a deactivating member for an engine combustion chamber valve. The electro-hydraulic actuator of the present invention includes a bleed passage above the bores for bleeding air from the system upon the depressurization of the piston bores. The electro-hydraulic actuator of the present invention thus enables a single solenoid operated valve to deactivate a hydraulically powers a plurality of actuators for deactivating a plurality of combustion chamber valve mechanisms.